Originally Posted by
sailorbenjamin
What sort of accuracy were you getting on length? I figure I'm within half a centimeter. Getting the angles was hard. I made a little jig. I should show it.
I did build a fork alignment jig. I've used it to measure several of these bikes. I'll get pics of that up, too.
Getting within 5 mm is not that difficult, but when you take those dimensions into a CAD program that kind of tolerance makes you have to question where the error(s) are, the tolerance stack can get pretty big. For me, 5 mm is too big a tolerance to "replicate" a bike by measure. 5mm at the seat tube end of the top tube can change the seat tube angle a half of a degree. The intersections of the top tube ends to the midpoints of the ST and HT are not the easiest. What I did was use a version of what Doug Fattic has described. It works very accurately. I agree that a fork jig will assist in getting accurate measurements.
Oh yeah, do not assume the top tube is level. Very often it is not.